Method and apparatus for switched physical alternate links in a packet network

ABSTRACT

A method and apparatus for improved operation of a packet network by controllably providing switched physical alternate links between packet network nodes, at least one of which is a host, and using those switched physical alternate links to supplement the capacity of the packet network. A switched physical alternate link is composed of physical elements, switchable connection devices, and a manager, such that a switched physical alternate link behaves as a single point-to-point physical link between nodes in a packet network. Creating and removing switched physical alternate links as the packet network operates provides supplemental carrying capacity between the packet network nodes connected by switched physical alternate links, while overall packet network congestion is simultaneously reduced.

FIELD OF THE INVENTION

[0001] The present invention relates to a method and an apparatus forswitched physical alternate data links that behave as singlepoint-to-point physical links between nodes in a packet network, toimprove network capacity and to reduce congestion.

DESCRIPTION OF THE PRIOR ART

[0002] A packet network typically comprises a plurality of hosts and atleast one router. The term “host” as used herein will refer to anydevice that primarily transmits and receives only its own traffic. Thusworkstations, PCs and servers are examples of hosts. The term “router”as used herein will refer to any device that is primarily used totransmit other devices' information. Thus Ethernet hubs, Fiber Channelswitches and Internet Protocol (IP) Routers are all examples of routers.

[0003] Physical connections in packet networks are typically from a hostto a router, or between routers. Direct host-to-host connections arealso possible, and create a network of exactly two hosts. In packetnetworks that include a router, each data packet that is transferredbetween hosts is first transmitted to a router, which determines whichhost or router to send that packet to next.

[0004] It is possible for a host to participate in more than one networkat the same time through different network interfaces.

[0005] Problems arise when a large flow of data packets is to betransmitted from one host to another host via a series of routers towhich other hosts are also connected. Such a large flow of data packetscan monopolize the available bandwidth on the links between the routersto such an extent that traffic between other hosts on the network isdisrupted. Viewed another way, the large flow of data packets may itselfbe disrupted or slowed by traffic between other unrelated hosts. Manysolutions have been created to mitigate this problem, either by managingthe sharing of bandwidth between hosts, or by increasing the carryingcapacity of the links between routers, examples from the PRIOR ARTincluding bandwidth management schemes, higher speed protocols (fastE,GigE, 10 GigE, increasing Optical Carrier speeds, etc and channelbonding (MLPPP, etc).

[0006] Schmidt in U.S. Pat. No. 6,366,951, issued in 2002, describes adistributed processing system where a management computer automaticallyconnects remote reduced-capability workstations with centralizedcomputing modules. The centralized workstations are switched on and offbased on how busy they are. Individual computer workstations areconnected with individual processing units by the management computer,and are disconnected when the link is no longer needed. In this system,the network is off-loaded when not busy. The system does not includeassignment of a dedicated link for transmission of large data packetflows in parallel with a conventional shared-use link.

[0007] Tse and McDowell in U.S. Pat. No. 6,345,052, issued in 2002,describe a localized sampling architecture for the reliable transitionof status signals from an interface device. The method that is describedillustrates traffic flow to and from hardware devices under heavytraffic conditions, and the need to assign both shared-use links andtime of use of said links.

[0008] Chiang in U.S. Pat. No. 6,336,156, issued in 2002, describesdynamic slot allocation for increased speed of initialization of amultiport switch. A scheduler increases the amount of bandwidthallocated to initialization logic; the amount of bandwidth allocated isthen decreased once the port has been initialized. During normaloperation of the switch, the scheduler allocates address table bandwidthto various components of the multiport switch.

[0009] McNamara in U.S. Pat. No. 6,262,976, issued in 2001, describes asystem and a method for network flow optimization using traffic classes.Classes of traffic include interior (within a packet network), interiorto exterior, exterior to interior, and transitory. A link is establisheddepending on the class of the traffic.

[0010] Story et al. in U.S. Pat. No. 6,260,092, issued in 2001, describea method of use of a fiber channel for serialized local bridging. Thesystem provides enhanced traffic loading thereby enhancing linkperformance in a point-to-point or ring connected network.

[0011] Dillon in U.S. Pat. No. 6,161,141, issued in 2000, describesnetwork system with TCP/IP protocol spoofing. Dual paths are availablefor low speed and high speed communications. However, no provision ismade for switching between the paths based on the nature of the traffic,for example on the sizes of data packet flows.

[0012] Schemes also exist for managing the physical paths over whichpacket data is transferred. Examples include the Hikari Router, asdescribed by Sato et al. in IEEE Communications Magazine March 2002 pp96-101, which uses GMPLS to create wavelength paths between routers, andby Jukan and Franzl in “Constraint-based path selection methods foron-demand provisioning in WDM networks”, IEEE INFOCOM conference, June2002; and references cited in this paper.

[0013] What is needed is a means for transmitting large data packetflows between hosts and, optionally, other selected nodes, in a packetnetwork in an uninterrupted, secure, and rapid manner while allowingother/normal traffic simultaneously to be transmitted over the packetnetwork, without either type of transmission adversely affecting theother.

SUMMARY OF THE INVENTION

[0014] The present invention is a system for providing switched physicalalternate links between nodes in a packet network, where at least one ofthe nodes is a host, and using those switched physical alternate linksto supplement the capacity of the packet network between those nodes.

[0015] A switched physical alternate link, or “SPAL”, comprises physicalelements and switchable connection devices, such that a SPAL behaves asa single point-to-point physical link between two nodes (host to host,or host to router) in a packet network.

[0016] Creating and removing SPALs as the packet network operatessupplements carrying capacity between the packet network hosts connectedby SPALs, while overall packet network congestion is simultaneouslyreduced, thereby providing superior performance capability when comparedwith the capabilities of PRIOR ART packet networks.

[0017] A set of hosts and optionally routers that are able tocommunicate to one another across a PRIOR ART packet network, and whichare also able to have a SPAL created between some or all pairs of them,are called “SPAL Nodes”. A current implementation uses a softwareprocess called the SPAL Client Software, which runs in each SPAL Nodeand controls one end point of each SPAL.

[0018] A SPAL Manager is a software and/or hardware device thatcommunicates with some or all SPAL Nodes, and creates and destroys SPALsaccording to at least one configurable criteria.

[0019] A SPAL Network is comprised of two or more SPAL Nodes, which maycontain SPAL Client Software, the equipment that comprises the SPALs,and one or more SPAL Managers.

[0020] A SPAL Manager may be requested to create a SPAL by one or moreof the SPAL Nodes, or the SPAL Manager might receive some externalrequest to create a SPAL, possibly based on a criterion such as a timeof day, a reservation system, a request from a human operator, or otherinternal or external event.

[0021] Soon after a SPAL is created, a SPAL Manager directs the SPALNode at each end of the SPAL to direct traffic over the newly createdSPAL. Prior to destroying a SPAL, a SPAL Manager directs the SPAL Nodesat each end of that SPAL to cease directing traffic over that SPAL. Inan Internet Protocol packet network, traffic can be directed byinserting or deleting appropriate entries in the IP Routing Table, in amanner that will be readily apparent to one skilled in the art.

[0022] The SPAL Network can automatically determine when to request aSPAL by monitoring network traffic for one or more specificcharacteristics, called “criterion characteristics”. Criterioncharacteristics include the following non-limiting examples: size ofpacket flow; packet flow rate; destination; time of day; user policy;type of data. One embodiment of the system has shown that the SPALClient Software can be used to monitor network traffic for criterioncharacteristics, however in principal this monitoring could be doneelsewhere within the packet network.

[0023] The set of criteria that are monitor for, and their specificattributes, can be modified by a management interface. This allows theset of criterion characteristics that are in effect to change over time.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024]FIG. 1 is a schematic representation of a packet network having anapparatus for creating switched physical alternate links overlainthereon.

[0025]FIG. 2 is an illustration of the effect of transmission of largedata packet flow along a link having a limited capability for an amountof data that can be transmitted within a given length of time.

DESCRIPTION OF THE INVENTION

[0026] A packet network system 10 having an apparatus 12 overlaidthereon for creating switched physical alternative links (SPAL) will bedescribed with reference to FIGS. 1 and 2.

[0027] Referring to FIG. 1, packet network 10 typically comprises aplurality of hosts 14, at least one router 16 and a plurality of links18 connecting each of hosts 14 with one of routers 16. Packet network 10can be a complex packet network comprised of several clusters 28, eachcluster having at least one host 14 and router 16. A complex packetnetwork 10 having two clusters 28 is illustrated schematically inFIG. 1. In complex packet network 10, routers 16 are linked via links30.

[0028] Apparatus 12 comprises at least one switch 20, a plurality ofcommunication links 22 that connect selected hosts 14 individually withswitch 20. Optionally, selected routers 16 also are connected viaadditional communication links 22 with switch 20. Selected hosts 14 andselected routers 16 connected to switch 20 are “SPAL Nodes” 214. Atleast one SPAL Manager 24 is in communication with each of SPAL Nodes214. SPAL Manager 24 includes a software program that manages trafficbetween SPAL Nodes 214 via apparatus 12. Optionally, said softwareprogram is SPAL Client software installed in SPAL node 214.

[0029] When traffic is to be sent from one of SPAL Nodes 214 to anotherof SPAL Nodes 214, software installed in one of SPAL Nodes 214 and themanager monitors said traffic to determine at least one criterioncharacteristic of data flow for transmission of said traffic in order todetermine whether a need exists for a SPAL. Said criterioncharacteristic may be, as non-limiting examples: size of packet flow;packet flow rate; destination; time of day; user policy; type of data.When said characteristic matches pre-programmed criteria, SPAL Manager24 determines that said traffic is to be transmitted via apparatus 12instead of via links 18 of packet network system 10. When saidcharacteristic does not match pre-programmed criteria, SPAL Manager 24determines that said traffic is to be transmitted via packet networksystem 10. Also, traffic is transmitted via packet network 10 instead ofvia apparatus 12 in response to other events caused by situationsinternal to apparatus 12, packet network 10, or as a default setting.

[0030] As one example of the criteria that may be established for use ofapparatus 12, the effect of traffic flow size will be illustrated withreference to FIG. 2.

[0031] When packet network 10 is used without apparatus 12, a limitationon use of packet network 10 occurs when large data packet flow rates areto be transmitted between hosts 14 along links 18 via router 16.Referring to FIG. 2, the time-performance 100 of packet network 10 isshown in which data packet flows 102 having different sizes 104 aretransmitted at different times 106.

[0032] Links 18 have a maximum rate 108 at which data can betransmitted. When a small amount of data 110 is to be transmittedbetween hosts 14, and a rate 112 at which said data is transmittable islower than maximum rate 108, an elapsed time 114 for transmission ofsaid small packet flow rate 110 has a low value. In contrast, when alarge amount of data 116 is to be transmitted, the rate 118 at whichsaid hosts 14 can transmit data may exceed maximum rate 108. In thiscase, the data packet flow rate cannot exceed maximum rate 108 and so anelapsed time 120 for transmission of said large data packet flow rate116 is large when compared with a theoretical elapsed time 122 fortransmission of large amount of data 116 at rate 118. Because elapsedtime 120 for transmission of large amount of data 116 is large,communication of other data packet flows 102 along links 18 is eitherdelayed or prevented, thereby causing inconvenience or delays. Inextreme cases, communication between hosts 14 via router 16 may beseverely compromised.

[0033] To circumvent the inconveniences to packet network 10 caused by,for example, traffic requiring large flow rates, such traffic isdiverted via apparatus 12, as follows.

[0034] When traffic is to be transmitted via apparatus 12, SPAL Manager24 establishes a SPAL comprising at least one switch 20 andcommunication links 22. Said SPAL then behaves as a singlepoint-to-point physical link between one SPAL Node 214 and another SPALNode 214. The point-to-point physical link so established is dedicatedbetween one SPAL Node 214 and another SPAL Node 214 for the durationrequired for complete transmission of said traffic.

[0035] When a SPAL has been created, a SPAL Manager 24 directs the SPALNode 214 at each end of the SPAL to direct traffic over the newlycreated SPAL. Prior to destroying a SPAL, a SPAL Manager directs theSPAL Nodes 214 at each end of that SPAL to cease directing traffic overthat SPAL. In an Internet Protocol packet network, traffic can bedirected by inserting or deleting appropriate entries in the IP RoutingTable, in a manner that will be readily apparent to one skilled in theart.

[0036] The SPAL Network can automatically determine when to request aSPAL by monitoring network traffic for one or more criterioncharacteristics. In the implementation of the system described herein,the SPAL Client Software monitors network traffic for criterioncharacteristics, but it will be recognized by those skilled in the artthat this monitoring could be done elsewhere within the packet network.

[0037] The set of criteria that are monitored, and their specificattributes, can be modified by a management interface. This allows theset of criterion characteristics that are in effect to change over time.

[0038] Establishment of said point-to-point physical link via apparatus12 provides advantages including:

[0039] network capacity is enhanced by availability of apparatus 12;

[0040] congestion in packet network 10 is reduced by providing alternatelinks for transmission of traffic;

[0041] routing is host-to-host, by-passing one or more routers and/orswitches;

[0042] traffic requiring large data flow rates is transmitted betweenone host 14 and another host 14 via a SPAL established using apparatus12 in an uninterrupted manner; and

[0043] traffic is transmitted between one host 14 and another host 14via a SPAL established using apparatus 12 with enhanced security becausethe point-to-point physical link so established is a dedicated link.

[0044] Apparatus 12 provides further advantages for transmission oftraffic between hosts in network 10 when plurality of communicationlinks 22 that connect each of hosts 14 with switch 20 are each opticallinks.

[0045] Apparatus 12 provides even further advantages for transmission oftraffic between hosts in network 10 when switch 20 is an optical switch,so that apparatus 12 is an all-optical system. Said further advantagesinclude improved quality of communication of traffic and advantagesaccruing from use of optical data management methods, as will berecognized by those skilled in the art.

1. A method of providing switched physical alternate links (SPAL) thatbehave as point-to-point physical links between nodes in a packetnetwork, comprising: providing an apparatus that is overlaid on thepacket network, comprising: at least one switch; communication linksconnecting selected nodes in the packet network with the at least oneswitch, the nodes being selected from among hosts and routers of thepacket network, the links being selected from among optical fiber links,optical wavelength links, electrical links, optical free-space links,other links, and a combination selected from among optical fiber links,optical wavelength links, electrical links, optical free-space links andother links; at least one manager that manages traffic between nodes viathe apparatus; and at least one management software program for managingtraffic between nodes via the apparatus; the management software programidentifying the need for SPAL, based on at least one of selected trafficcharacteristics, external command, and other selected criteriaincluding: time, permission, application, target address; creating andallocating a SPAL for said traffic; causing said traffic to flow overthe SPAL; determining when the SPAL is no longer required, based on atleast one of selected traffic characteristics, external command, andother selected criteria including: time, permission, application, targetaddress; removing said traffic from the SPAL; and deallocating the SPAL.2. The method according to claim 1, in which the nodes linked by theSPAL are hosts.
 3. The method according to claim 1, in which one of thenodes is a host and another of the nodes is a router that are linked bythe SPAL.
 4. The method according to claim 1, in which the managementsoftware program is a SPAL Client software program that monitors trafficand controls routing at a node.
 5. The method according to claim 1, inwhich the at least one switch is an optical circuit switch.
 6. Themethod according to claim 1, in which the management software program isused to: determine that a SPAL is required for traffic between one nodeand another node; determine that a SPAL can be created between the onenode and the another node between which the SPAL is required; establisha point-to-point link between the one node and the another node;allocate that point-to-point link to transmission of data between theone node and the another node for the duration required for transmissionof the traffic; and deallocate the point-to-point link followingtransmission of the traffic.
 7. The method according to claim 1, inwhich the manager acts on request to create and allocate the SPAL thatbehave as single point-to-point physical links between hosts.
 8. Themethod according to claim 1, in which the manager deallocates links uponcompletion of transmission of traffic to which the SPAL that behave assingle point-to-point physical links between hosts have been allocated.9. An apparatus that is overlaid onto a packet network to provideswitched physical alternate links (SPAL) that behave as singlepoint-to-point physical links between nodes in the packet network, toimprove network capacity and reduce congestion, The apparatuscomprising: at least one switch; communication links connecting selectednodes in the packet network with the at least one switch, the nodesbeing selected from among hosts and routers of the packet network, thelinks being selected from among optical fiber links, optical wavelengthlinks, electrical links, optical free-space links, other links, and acombination selected from among optical fiber links, optical wavelengthlinks, electrical links, optical free-space links and other links; atleast one manager; and at least one management software program formanaging traffic between nodes via the apparatus.
 10. The apparatusaccording to claim 9, in which the nodes linked by the SPAL are hosts.11. The apparatus according to claim 9, in which one of the nodes is ahost and another of the nodes is a router that are linked by the SPAL.12. The apparatus according to claim 9, in which the management softwareprogram is a SPAL Client software program that monitors traffic andcontrols routing at a node.
 13. The apparatus according to claim 6, inwhich the at least one switch is an optical circuit switch.
 14. Theapparatus according to claim 9, in which the manager includes a programthat is used to: determine that a SPAL is required for traffic betweenone node and another node; determine that a SPAL can be created betweenthe one node and the another node between which the SPAL is required;establish a SPAL as a point-to-point link between the one node and theanother node; allocate that point-to-point link to transmission of databetween the one node and the another node for the duration required fortransmission of the traffic; and deallocate the point-to-point linkfollowing transmission of the traffic.
 15. The apparatus according toclaim 9, in which the manager acts on request to create and allocate theSPAL that behave as single point-to point physical links between nodes.16. The apparatus according to claim 15, in which the managerdeallocates links upon completion of transmission of traffic to whichthe SPAL that behave as single point-to-point physical links betweennodes have been allocated.
 17. The apparatus according to claim 9, inwhich the SPAL are temporarily switched using one of an opticalcross-connect switch, an electrical switch, and a mechanical switch. 18.The apparatus according to claim 9, in which the switch is controlled ata node that is an end-point.
 19. An apparatus that is overlaid onto apacket network to provide switched physical alternate links (SPAL) thatbehave as single point-to-point physical links between nodes in thepacket network, to improve network capacity and reduce congestion, theapparatus comprising: at least one switch; communication linksconnecting selected nodes in the packet network with the at least oneswitch, the nodes being selected from among hosts and routers of thepacket network, the links being selected from among optical fiber links,optical wavelength links, electrical links, optical free-space links,other links, and a combination selected from among optical fiber links,optical wavelength links, electrical links, optical free-space links andother links; and at least one manager; at least one management softwareprogram for managing traffic between nodes via the apparatus; the SPALbeing temporarily switched using at least one of an opticalcross-connect switch, an electrical switch, and a mechanical switch; theswitch being controlled at an end-point; the manager acting on requestto create and allocate the SPAL that behave as single point-to-pointphysical links between nodes; and the management software program beingused to: determine that a SPAL is required for traffic between one nodeand another node; determine that a SPAL can be created between the onenode and the another node between which the SPAL is required; establisha SPAL as a point-to-point link to transmission of data between the onenode and the another node for the duration required for transmission ofthe traffic; and deallocate the point-to-point link followingtransmission of the traffic; and deallocate links upon completion oftransmission of traffic to which the SPAL that behave as singlepoint-to-point physical links between nodes have been allocated.
 20. Themethod according to claim 19, in which the nodes linked by the SPAL arehosts.
 21. The method according to claim 19, in which one of the nodesis a host and another of the nodes is a router that are linked by theSPAL.
 22. The method according to claim 19, in which the managementsoftware program is a SPAL Client software program that monitors trafficand controls routing at a node.